Answering your first question, because I've done this:
Two scanners/moving heads, drawing circles, 1 clockwise, 1 counter clockwise. The answer is "yes". I was discussing this with Jingles and he said to play with the phase setting to get the effect I wanted. Worked great. I am in fact using this.
2 scanners moving down while 2 moving up? Perhaps. Not sure on this one. If you have them take the same number of steps, you can always manually add the opposite to the other scene. Say, let's say you go "down to up" in 6 steps, then "up to down" in 6 steps, you can just document and then manually make a new scene. Copy one, then manually input the values for the opposite direction. That would be the worse case scenario.
The reason I am not as confident on your second scenario is I only have 2 moving head lights, so I can't test with 4. But, here's a good thing: it doesn't really matter if you have them or not, you can design what you want using the 3D Visualizer and it seems to be as accurate as I need it to be.
Also, you can download and evaluate MyDMX for free. If you choose to purchase MyDMX, then you get the USB interface/dongle that is necessary for you to be able to actually use MyDMX to control your lights.